'en pnuemati' is translated as "in Spirit" in John 4:24, yet in Ephesians 5:18, it is translated as "with Spirit". Does anyone know why ?

I understand that the preposition 'en' when it comes before a dative noun case ('pnuemati') is always rendered as "in" not "with". "With" tells us the mode by which something is done, whereas "in" tells us the location.

First off, a little housekeeping. To post on B-Greek, you need to use your real name as your user name. If you send your name to jonathan dot robie at ibiblio dot org, I will change it for you.

On to your question. Prepositions are tricky, and the simple rule you gave doesn't really describe all the possible meanings of ἐν. Consider the different ways that ἐν πνεύματι is translated in different verses and translations:

What grammar are you learning from? It probably has a summary of different meanings of the preposition ἐν. As a beginner, the simplest thing might be to take a list of common meanings, like the ones suggested here:

lion wrote:'en pnuemati' is translated as "in Spirit" in John 4:24, yet in Ephesians 5:18, it is translated as "with Spirit". Does anyone know why ?

I understand that the preposition 'en' when it comes before a dative noun case ('pnuemati') is always rendered as "in" not "with". "With" tells us the mode by which something is done, whereas "in" tells us the location.

I think it is quite safe to say that "εν" always goes with the dative case in Koine Greek, so the case of the noun phrase is not relevant. "εν" is used in many different ways, mainly with the meaning "in / among" (position) or "in / by" (indirect agent), but also "in" (with respect to / according to) or "in" (some period of time) or "at" (a particular point in time)... The actual meaning can only be determined in each context, and is subject to each one's interpretation. Also do not take the English word as an accurate representative of the original preposition, because while it may accurately represent it in one instance, it would not work in another, because the range of the English preposition is different from the range of the Greek preposition.

Some (http://www.crosswire.org/study/parallel ... hn+4:23#cv) take "εν πνευματι" in John 4:23-24 to mean "in spirit" (which I believe fits the whole sentence best) while others take it to mean "by [the] spirit [of God]" (which is also possible because the article is very often omitted when referring to "the spirit of God").

In Eph 5:18 however it is much clearer because it is in parallel with "μη μεθυσκεσθε οινω" / "do not be made drunk [by] wine" and so "πληρουσθε εν πνευματι" should therefore mean "be fully filled by [the] spirit".